# std::bad_any_cast

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< cpp‎ | utility‎ | any

Defined in header `<any>` |  |
class bad_any_cast : public std::bad_cast; |  | (since C++17)

Defines a type of object to be thrown by the value-returning forms of std::any_cast on failure.

### Member functions

(constructor) | constructs a new `bad_any_cast` object (public member function)
operator= | replaces the `bad_any_cast` object (public member function)
what | returns the explanatory string (public member function)

## std::bad_any_cast::bad_any_cast

bad_any_cast() noexcept; | (1) | (since C++17)
bad_any_cast( const bad_any_cast& other ) noexcept; | (2) | (since C++17)

Constructs a new `bad_any_cast` object with an implementation-defined null-terminated byte string which is accessible through `what()`.

1) Default constructor.
2) Copy constructor. If *this and other both have dynamic type `std::bad_any_cast` then std::strcmp(what(), other.what()) == 0.

### Parameters

other | - | another exception object to copy

## std::bad_any_cast::operator=

bad_any_cast& operator=( const bad_any_cast& other ) noexcept; |  | (since C++17)

Assigns the contents with those of other.If *this and other both have dynamic type `std::bad_any_cast` then std::strcmp(what(), other.what()) == 0 after assignment.

### Parameters

other | - | another exception object to assign with

### Return value

*this

## std::bad_any_cast::what

virtual const char* what() const noexcept; |  | (since C++17)

Returns the explanatory string.

### Return value

Pointer to an implementation-defined null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring. The pointer is guaranteed to be valid at least until the exception object from which it is obtained is destroyed, or until a non-const member function (e.g. copy assignment operator) on the exception object is called.

The returned string is encoded with the ordinary literal encoding during constant evaluation. | (since C++26)

### Notes

Implementations are allowed but not required to override `what()`.

## Inherited from std::bad_cast

## Inherited from std::exception

### Member functions

(destructor) [virtual] | destroys the exception object (virtual public member function of `std::exception`)
what [virtual] | returns an explanatory string (virtual public member function of `std::exception`)

### Example

Run this code

    #include <any>
    #include <cassert>
    #include <print>

    int main()
    {
        auto x = std::any(42);
        assert(std::any_cast<int>(x) == 42); // OK

        try
        {
            [[maybe_unused]] auto s = std::any_cast<std::string>(x); // throws
        }
        catch (const std::bad_any_cast& ex)
        {
            std::println("{}", ex.what());
        }
    }

Possible output:

    bad any_cast

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